Activator compositions and their use in emulsion polymerization



Patented Oct. 14, 1952 ACTIVATOR. COMPOSITIONS AND THEIR USE IN EMULSIONPOLYMERIZATION Carl A. Uraneck and Willard M. St. John, Borger, andCharles F. Fryling andJames E. Troyan, Phillips, Tex., assignors toPhillips Petroleum Company, a corporation of Delaware No Drawing.Application December 31, 1948, Serial No. 68,720

20 Claims. 1

This invention relates to polymerization of conjugated diolefins inaqueous emulsion. In one embodiment it relates to preparing syntheticrubber by emulsion polymerization using a highly active and stableactivator system.

In the production of rubber-like elastomers various polymerizationrecipes have been developed in order to provide polymers of superiorphysical properties. Variations in operating techniques have also beenintroduced in order to effect further improvements in the properties ofthe product. Recent developments have shown thatsynthetic elastomershaving greatly improved properties may be obtained if polymerizationreactions are effected at low temperatures. Since conversion ratesgenerally decrease rapidly as the temperature is decreased, fasterrecipes are necessary in order that these reactions may be carried outon a practical basis. In order to accomplish the desired results atlower temperatures, a number of polymerization recipes have beenprovided. Outstanding among these are those in which a peroxide orhydroperoxide is a key component, and those in which a diazothioether isa key component. The peroxides and hydroperoxidesare usually used inredox recipes, which include a combination of an oxidant, a reductant,and an oxidation catalyst. In this type of recipe the peroxide orhydroperoxide is the oxidant. The oxidation catalyst is generallyselected from a group of materials consisting of compounds of metalssuch as iron, manganese, copper, vanadium, cobalt, etc. In general it'isassumed that the metal must be a multivalent metal and in such acondition that it can change its valence state reversibly; The otheringredient ordinarily present is a reductant, and is usually an organicmaterial such as a reducing sugar or other easily oxidizable polyhydroxycompound. Compounds frequently employed in this capacity are glucose,levulose, sorbose, invert sugar, and the like. As the oxidant insuch arecipe, there may be used an inorganic pefdxide, such as hydrogenperoxide, a pernitrate. a perfsulfate, a permanganate, or the like, oran organic peroxide such as benzoyl peroxide, or an organichydroperoxide such as tertiary butyl hydroperoxide, methyl cyclohexylhydroperoxide, or cumene'hydroperoxide (more formally designateddimethyl(phenyDhydroperoxymethane) In another type of recipe adiazothioether is the key component, and while it may be used alone, itis preferably used in combination with a water-soluble ferricyanidewhich is a salt of a monovalent cation, such as ammonium or an alkalimetal. In all of these recipes, it is usually desirable to include amodifier, such as a mercaptan, and an emulsifying agent.

We have found that the oxidation catalyst used in such polymerizationrecipes is a very important part of the recipe, and that certainspecific improvements in its preparation result in markedly increasingthe rate of polymerization and frequently also favorably influence thecharacteristics of the reaction mixture. Usually this oxidation catalystcomprises a compound of a multivalent metal such as iron, manganese,copper, vanadium, cobalt, and the like, and most commonly is awater-soluble iron salt. The multivalent metal ion of such compounds canreadily pass from a low valence state to a higher valence state, andvice versa. Sometimes the compound, when present in its lower valencestate, can function in the dual role of reductant and oxidationcatalyst.

One commonly used redox catalyst is iron pyrophosphate. In a redoxsystem comprising hydrogen peroxide and organic mercaptan, used asoxidant and reductant respectively, ferric pyrophosphate, prepared byaddition of a ferric salt to an aqueous solution of sodiumpyrophosphate. has been found to be a useful catalyst. With anotherclass of redox systems, comprising a cumene hydroperoxide and sugar,ferrous pyrophosphate has been found to be more efiective as a catalyst,as i more fully discussed in Kolthoff application Serial No. 751,955,filed June 2, 1947. However, ferric pyrophosphate can also be used. Whencarrying out a polymerization with the ferrous system, certaindifficulties are encountered. For example, if the catalyst is preparedin the form of a so-called' activator solution by adding ferrous sulfateto an aqueous solution of sodium pyrophosphate, the solution must beused immediately, otherwise oxidation by the atmosphere destroys itspotency. Impurities in the water, such as calcium salts, etc., likewiseare deleterious. If the concentration of ferrous ion added to the systemis greater than the concentration of cumene hydroperoxide, i. e., ifthere is present more than one gram, or milligram, ion of ferrous ionper gram, or milligram, molecule of cumene hydroperoxide, nopolymerization occurs. The excess of cumene hydroperoxide required foroptimum operating conditions over the mol ratio of one to one is solittle that slight errors in measurement of these ingredients can easilycause great differences in the rate of polymerization and in the extentto which polymerization proceeds. However, it should be emphasized thatif care is exercised in preparing the activator solution, consistent andhigh rates of polymerization can be obtained.

In preparing activator solutions, a ferrous or ferric salt is added to asolution of sodium pyrophosphate. Ferrous and ferric pyrophosphate areformed by metathesis and these compounds combine further to formpyrophosphate complexes, such as the well known soluble ferricpyrophosphate, Fe4(P207)3-3Na4P20'z-$H20. For this reason it has becomecustomary to speak of ferrous pyrophosphate and ferric pyrophosphateactivators without specifying the source of the ferrous or ferric ions,that is, whether derived from ferrous sulfate or some other salt, andwithout specifying to what extent the resulting pyrophosphates have beencomplexed. It can be mentioned that.

the aforementioned "soluble ferric pyrophosphate has been found to be avery convenient source of ferric ions for the preparation of ferricactivators.

With ferrous pyrophosphate, a molecular excess of cumene hydroperoxidewith respect to ferrous ion must be present to obtain anypolymerization. With ferric pyrophosphate, on the other hand, thislimitation is absent and polymerization can be conducted with amounts ofcumene hydroperoxide which are much lower than are required with anequivalent concentration of ferrous salt. However, under the bestattainable conditions the rate of polymerization is never faster thanabout 67 per cent of what can be obtained with ferrous pyrophosphate. Itmight be thought that a mixture of ferrous and ferric salts wouldpossess certain advantages and such indeed has been found to be thecase. With such mixtures the limiting ratio of cumene hydroperoxide toiron can be lowered without adversely affecting the high rates ofpolymerization obtainable with ferrous pyrophosphate activation.

We have now found that, when an emulsion polymerization of a conjugateddiolefin is carried out to produce synthetic rubber in a systemcontaining an oxidant and an oxidation catalyst such as just discussed,surprising improvements are obtained in the polymerization rate, andalso often fluidity of the resulting latex, when certain water solublesalts are incorporated in a particular manner in the activator solutionwhich contains the oxidation catalyst. According to our invention, theactivator solution is prepared by dissolving in water a salt of amultivalent metal such as previously discussed, a pyrophosphate ofamonovalent cation, such as an alkali metal or ammonium, and a differentsalt of a monovalent cation and an anion which is inert with respect tothe first named multivalent metal salt. This last compound is alsopreferably a salt of an alkali metal or ammonium, and the anion shouldneither tend to oxidize the multivalent metal ion when it is present inits lower valence state nor reduce it when it is present in its highervalence state nor precipitate it, when in either valence state, fromaqueous solutions such as are commonly used in emulsion polymerization.We prefer to prepare the activator solution with the multivalent metalin its lower valence state, and in such instances the use of a separatereductant in the polymerization system is frequently unnecessary,particularly when operating at subfreezing polymerization temperaturewith an alcohol present in the aqueous medium. When the activatorsolution is prepared with a salt of a multivalent metal in its highervalence state it is usually necessary also to have a reductant, such asa reducing sugar,

present while the solution is heated. If desired such a reductant mayalso be present when the multivalent metal is present in its lowervalence state. The third salt which is added can be any one of. a largenumber of .salts which meet the foregoing requirements, and a salt of amonovalent ion which is a fluoride, chloride, nitrate, sulfate,phosphate, borate, tetraborate, formate, acetate, propionate, benzoate,tartrate, salicylate, citrate, and the like, is particularly preferred.In order to get our improved results to the greatest extent it isnecessary to add the multivalent metal salt, pyrophosphate, and thirdsalt to Water and then to heat the resulting solution to atemperaturebetween 40 and C. The solution should be heated out ofcontact with free oxygen, as by boiling or heating in a nitrogenatmosphere, and subsequently kept from such contact. After cooling, itis then added to the reaction mixture as desired. As is illustrated bydata in Examples VII and VIII, other methods of incorporating theseingredients in the reaction system are markedly less effective.

An object of this invention is to polymerize unsaturated organiccompounds. Another object of this invention is to produce an improvedsynthetic rubber. Still another object of this invention is to increasethe reaction rate in polymerizing unsaturated organic compounds inaqueous emulsion. An additional object of this invention is to produce amore fluid synthetic rubber latex when effecting emulsion polymerizationat subfreezing temperatures. Still another object of thisinvention is toproduce a more active activator solution for use in emulsionpolymerization, where an oxidant is an essential ingredient of thepolymerization mixture. Further objects and advantages of this inventionwill become apparent, to one skilled in the art, from the accompanyingdisclosure and discussion.

In effecting emulsion polymerization of a monomeric material,particularly when a batch-type or semibatch-type operation is carriedout, the reactor is usually first charged with the aqueous medium, whichcontains the desired emulsifying agent, and the monomeric material isthen admixed with agitation of the contents. At the same time a,reaction modifier, such as a mercaptan, is also included, usually insolution in at least a part of the monomeric material. An activatorsolution and an oxidant are separately added to the reaction mixture,and reaction then proceeds. A preferred manner of adding these twoconstituents is usually to have the activator solution incorporated inthe aqueous medium prior toaddition of the monomeric material, and toadd the oxidant as the last ingredient. Sometimes, however, satisfactorypolymerization results can be obtained when this procedure is reversed.It is also sometimes the practice to add portions of one or the other ofthe activator solution and oxidant intermittently, or continuously,during the course of the reaction. If the operation is carried outcontinuously, streams of the various ingredients are admixed insomewhat. the same order prior to their final introduction into thepolymerization reaction zone.

The activator solution which is prepared in accordance with ourinvention is usually prepared entirely separately and somewhat prior toits use in the polymerization reaction. Each ingredient is dissolved inwater in a concentration between about 0.1 and 10 parts by weight per100 parts of water used for the activator solution. The three essentialingredients hereinbefore discussed are added to water and the resultingsolution heated to a temperature between 40 and 100 C., preferablybetween 50 and 80 C., for a period of from 5 to 90 minutes, more usuallyfrom 30 to 60 minutes. This heating and subsequent handling of thesolution should be done in the absence of free oxygen. If the solutionis heated to boiling, the resulting steam is .frequently suflicient todrive off any air, and free oxygen can thus be excluded from theactivator system. If a lower temperature is used, it is frequentlynecessary to introduce a stream of an inertgas, such as nitrogen-overthe surface of the'liquid, and to maintain such an inert atmosphere inthe vapor phase of any container in which the liquid is stored. In themajority of cases, the salt of the multivalent metal and thepyrophosphate are present in an amount ranging from 0.8 to 1.2 mols withrespect to one mol of the other,'iand the resulting activator solutionand oxidant are subsequently added to the polymerization zone in amountsso that the relative amounts of these materials are within the samerange. It is usually preferred that the amounts of multivalent metalionand pyrophosphate be present in equimolar. quantities, and the amountof oxidant be in excess of the molecular equivalent of the multivalentmetal and pyrophosphate. We prefer to see to it that the strength ofouractivator solution is so regulated, and the amount of the activatorsolution added is so regulated, that there is added to the reactionmixture from 0.01- to 3 millimol parts of multivalent metal andpyrophosphate and oxidant per 100 parts by weight of monomericmaterial,with the preferred quantities being in the range from 0.1 to0.65 millimol parts by weight of multivalent metal. The amount of thethird salt added is between 0.1 and 5 parts per 100 parts of monomericmaterial, and often is not more than 0.5 part. In considering theamounts of these materials, the same units of weight should be used.That is, if the monomeric material is measured in pounds, these othermaterials are measured in millipound mols.

As previously stated, it is usually desirable that the multivalent metalbe present in its lower valence state. With some recipes, it isunnecessary to include an organic reducing agent either in the activatorsolution or in the polymerization mixture. However, particularly attemperatures abov 0 C., a faster reaction is sometimes obtained withsome recipes when a small amount of an organic reducing agent, such as areducing sugar, is included in the polymerization recipe, and it isfrequently more desirable to incorporate this in the reaction system byfirst including it in the activator solution along with the otheringredients. When the multivalent ion is present in its higher valencestate, it is usually necessary to include in the activator solution anorganic reducing agent. As a result the multivalent ion will bepartially reduced and a substantial amount of the multivalent ion willbe present in its lower valence state when the activator solution isready for addition to the polymerization mixture.

It is usually preferred that the multivalent ion be iron, and theactivator solution may be prepared from any of the readily availablesoluble iron salts, such as ferrous sulfate, ferric sulfate, ferrousnitrate, and the like. A pyrophosphate of sodium or potassium is alsousually used in preparing the activator solution. Apparently the ferroussalt and the pyrophosphate inter-react to form some kind of a complexcompound, and it may be that the third salt, which-we include in theactivator solution prior to being heated, influence in some way thecomposition or molecular structure of the resulting complex. Previousexperience with the preferred types of recipes has indicated that it isnecessary to incorporate at least 0.3 part by weight of iron salt in thereaction mixture per parts of monomers in order to obtain satisfactoryreaction rates and conversions. This corresponds to at least. about 1.1millimol parts of ironper 100 parts of monomers charged to thereactionsystem. We have discovered that when the activator solution isprepared as disclosed herein, satisfactory results can be obtained withan amount of iron no greater than 0.2 millimol parts per 100 parts ofmonomers charged. As a result, the final polymer product contains asubstantially lower quantity of iron, which is distinctly desirableinsofar as the properties of the resulting rubber product are concerned.This is particularly true when a salt such as potassium chloride orsodium fluoride is included in preparing the activator system in themanner described.

One point of major concern when carrying out emulsion polymerizationreactions at low temperatures, particularly at subfreezing temperatures,is that of having the latex become very viscous, or even set up to forma gel. An additional advantage which results from the use of ourinvention, and which results particularly when the salt added to theactivator system is potassium chloride or a fluoride or a tetraborate,is that the resulting latex produced when the activator solution is usedis highly fluid and free from gelation tendencies. Gelation of thelatex, precoagulation, and skin formation during polymerization, whichare frequently severe, are prevented when operating in the mannerdescribed with these two classes of salts. Since the polymerizationreaction is exothermic and it is necessary to both agitate the solutionto maintain adequate emulsification and to aid contact with coolingsurfaces to remove heat of reaction, this production of a highly fluidlatex makes agitation much easier, and aids in maintaining a moreuniform temperature during the reaction, as well as producing a latexwhich can be easily handled in subsequent process steps.

The monomeric material polymerized to produce polymers by the process ofthis invention comprises unsaturated organic compounds which generallycontain the characteristic structure CH2=C and, in most cases, have atleast one of the disconnected valencies attached to an electronegativegroup, that is, a group which increases the polar character of themolecule such as a chlorine group or an organic group containing-adouble or triple bond such as vinyl, phenyl, cyano, carboxy or the like.Included in this class of monomers are the conjugated butadienes or 1.3-butadienes such as butadiene (1,3-butadiene),2,3-dimethyl-1,3-butadiene, isoprene, piperylene, 3 furyl-l,3-butadiene,3-methoxy-1,3-butadiene and the like; haloprenes, such as chloroprene(2-chloro-1,3-butadiene), bromoprene methylchloroprene(2-chloro-3-methyl-1,3-butadiene), and the like; aryl olefins such asstyrene, various alkyl styrenes, p-chlorostyrene, p-methoxystyrene,alpha-methylstyrene, vinylnaphthalene and similar derivatives thereof,and the like; acrylic and substituted acrylic acids and their esters,nitriles and amides such as acrylic acid, methacrylic acid, methylacrylate, ethyl acrylate,

methyl alpha-chloro-acrylate, methyl methacrylate, ethyl methacrylate,butyl methacrylate, methyl ethacrylate, acrylonitrile,methacrylonitrile, methacrylamide and the like, methyl isopropenylketone, methyl vinyl ketone, methyl vinyl ether, vinylethinyl alkylcarbinols, vinyl acetate, vinyl chloride, vinylidene chloride,vinylfurane, vinylcarbazole, vinylacetylene and other unsaturatedhydrocarbons, esters, alcohols, acids, ethers, etc., of the typesdescribed. Such unsaturated compounds may be polymerized alone, in whichcase simple linear polymers are formed, or mixtures of two or more ofsuch compounds which are copolymerizable with each other in aqueousemulsion may be polymerized to form linear copolymers.

The process of this invention is particularly effective when themonomeric material polymerized is a polymerizable aliphatic conjugateddiolefin or a mixture of such a conjugated diolefin with lesser amountsof one or more other compounds containing an active CH2=C group whichare copolymerizable therewith such as aryl olefins, acrylic andsubstituted acrylic acids, esters, nitriles and amides, methylisopropenyl ketone, vinyl chloride, and similar compounds mentionedhereinabove. In this case the products of the polymerization are highmolecular weight linear polymers and copolymers which are rubbery incharacter and may be called synthetic rubber. Although, as can bereadily deduced from the foregoing, there is a host of possiblereactants, the most readily and commercially available monomers atpresent are butadiene itself (1,3-butadiene) and styrene. The inventionwill, therefore, be more particularly discussed and exemplified withreference to these typical reactants. With these specific monomers, it,is usually preferred to use them together, in relative ratios ofbutadiene to styrene between 65:35 and 90 by weight.

Alcohols which are applicable, when operating at low temperatures,comprise water-soluble compounds of both the monohydric and polyhydrictypes, and include methyl alcohol, ethylene glycol, glycerine,erythritol, and the like. The amount of alcoholic ingredient used in apolymerization recipe must be sufiicient to prevent freezing of theaqueous phase and generally ranges from 20 to 80 parts per 100 parts ofmonomers charged. In most cases the amount of water employed issufficient to make the total quantity of the alcohol-water mixture equal180 parts. In cases where it is desired to use a larger quantity of thealcohol-water mixture, say around 250 parts, the amount of alcohol maybe increased to as much as 120 parts. It is preferred that the alcoholbe such that it is substantially insoluble in the non-aqueous phase, andthat 90 per cent, or more, of the alcohol present be in the aqueousphase. A high-boiling alcohol such as glycerine is difficult to recoverfrom the resulting serum; a low-boiling alcohol such as methanol iseasily removed and frequently preferred. Other low-boiling alcohols suchas ethanol, however, are frequently too soluble in the liquid monomericmaterial to permit satisfactory operation. If the resulting latex tendsto gel at low reaction temperatures, a larger proportion of aqueousphase should be used. It is generally preferred that the emulsion be ofan oil in water type, with the ratio of aqueous medium to monomericmaterial between about 1.5:1 and about 2.75:1, in parts by weight. Inthe practice of the invention suitable means will be necessary toestablish and maintain an emulsion and to remove reaction heat tomaintain a desired reaction temperature. The polymerization may beconducted in batches, semicontinuously, or continuously. The totalpressure on the reactants is preferably at least as great as the totalvapor pressure of the mixture, so that the initial reactants will bepresent in liquid phase.

Emulsifying agents which are applicable in these low temperaturepolymerizations are materials such as potassium laurate, potassiumoleate, and the like. However, other emulsifying agents, such asnon-ionic emulsifyingv agents, salts of alkyl aromatic sulfonic acids,salts of alkyl sulfates, and the like which will produce favorableresults under the conditions of the reaction, can also be used inpracticing the invention.

The pH of the aqueous phase may be varied over a rather wide rangewithout producing deleterious effects on the conversion rate or theproperties of the polymer. In general the pH may be within the range of9.0 to 11.8, with the narrower range of 9.5 to 10.5 being most generallypreferred.

The mercaptans applicable in this invention are usually alkylmercaptans, and these may be of primary, secondary, or tertiaryconfiguration, and generally range from C8 to C16 compounds, but mayhave more or fewer carbon atoms per molecule. Mixtures or blends ofmercaptans are also frequently considered desirable and in many casesare preferred to the pure compounds. The amount of mercaptan employedwill vary, depending upon the particular compound or blend chosen, theoperating temperature, the freezing point depressant employed, and theresults desired. In general, greater modification is obtained whenoperating at low temperatures and therefore a smaller amount ofmercaptan is added to yield a product of a given Mooney value, than isused at higher temperatures. In the case of tertiary mercaptans, such astertiary C12 mercaptans, blends of tertiary C12, C14, and C16mercaptans, and the like, satisfactory modification is obtained with0.05 to 0.3 part mercaptan per 100 parts monomers, but smaller or largeramounts may be employed in some instances. In fact, amounts as large as1 part per 100 parts of monomers may be used. Thus the amount ofmercaptan is adjusted to suit the case at hand.

Temperatures applicable for the operation of this invention may rangefrom 40 to +70 C., with the range 20 to +5 C. being preferred.

Our new activator solutions can be'used to advantage in systems whereinthe oxidizing agent is a peroxidic-type material, ora, compound whichfunctions in the capacity of an oxidizing agent, such as adiazothioether which is soluble in a liquid hydrocarbon material, suchas liquid butadiene. We prefer to use organic peroxides andhydroperoxides, such as may be represented by the formula R'OOR", whereIt I lene,

, were varied.

9 1- (2,4-dimethylbenzene diazomercapto) naphthalene, and the like.

Advantages of this invention are illustrated by the following examples.The reactants, and their proportions, and the other specific ingredientsof the recipes are presented as being typical and should not beconstrued to limit the invention unduly.

Example I Butadiene and styrene were copolymerized, using the followingrecipe:

Parts by weight Butadiene '70 Styrene 30 Water (including that inactivator) 180 Methanol 40 Potassium laurate (95% neutralized) 5.0Mercaptan blend 0.12 Cumene hydroperoxide (100%) 0.17 (1.1 millimols)Activator solution 25 ml.

Ferrous sulfate (FeSO4-7H2O) 0.31 (1.1millimols) Sodium pyrophosphate(N3.4P20710H20)---.. 0.56 (1.25 millimols) Sodium fluoride 0.14 (3.3millimols) A blend of tertiary C C and C mercaptans in a ratio of 3 :1:1 parts by weight.

This solution was prepared by adding the three salts to water, in theproportions indicated, and heating the resulting solution to about 50 C.for 30 minutes, with the exclusion of air. The solution was then cooledout of contact with air.

Polymerization was effected at l C. for a period of 17.4 hours at whichtime a conversion of 84 per cent was reached. A substantially gelfree,fluid latex was produced.

A'parallel run was made'except that 0.70 part sodium pyrophosphate wasemployed and sodium'fluoride wasomitted. Conversion reached only 65 percent in 17.4 hours and the latex was highly viscous.

Example II Three parallel runs were made using the recipe and conditionsgiven in Example I except that in preparing the activator solution, theamounts of sodium pyrophosphate and sodium fluoride amounts of each ofthese ingredients are shown, together with the conversion obtained in a12.5- hour period using the resulting activator solutions.

I Conversion Run N0. F NaF, Parts Percent 7 12.5 Hours In run No. 2 thelatex was, fluid while in the other runs it was viscous. Similar resultsare produced when potassium fluoride is used in place of sodiumfluoride.

These data show clearly the improved conver sion rates obtained whenusing an activator system containing a soluble fluoride.

In the following tabulation the,

10 Erample III Butadiene and styrene were copolymerized using the followrecipe:

Parts by weight 1 Laurie acid, per cent neutralized with KOH. V "A blendof tertiary C12, C14, and C aliphatic mercaptans in a ratio of 3 :1 :1parts by weight..

The activator solution was prepared by heating a mixture of 2.2 gramsFGSO4.7H30, 4.0 grams Na4P2O'L10H2O, 1.0 gram Na2B40'z.5H20, andsuflicient water to make mL'for 40 minutes at 60 C. Polymerization waseffected at --10 C. for a period of 15.5 hours at which time aconversion of 77.8 per cent was reached. A parallel run containing 0.70part sodium pyrophosphate and no sodium tetraborate gave a conversion of65.8 per cent in 15.5 hours. i

In a third run the amounts of sodium pyrophosphate and sodiumtetraborate were changed in the following way:

nairzomomo 0.40 part (0.90 millimol NazB4O'z.5H-2O 0.30 part (1.03millimols) Polymerization was carried out at -10 (Las in the precedingruns. A conversion of 67.9 per cent was obtained in 15.5 hours.

In both cases where the activator contained sodium tetraborate the latexwas fluid, the fluidity being greater in the run containing the largerquantity of the tetraborate. In the run without the tetraborate thelatex set up tightly. The tetraborate-containing activators appearedmore stable to air oxidation than the control.

Example IV The following recipe was employed for carrying out abutadiene-styrene copolymerization at '10 C. e 1

Parts by weight Butadiene '70 Styrene 30 Water 192 Methanol 48 Potassiumlaurate (95% neutralized) 5.0 Mercaptan blend 0.25 Cumene hydroperoxide0.084 (0.55 millimol) Activator solution:

Ferrous sulfate,

FeSO4.'?HzO 0.139 (0.50 millimol) Sodium pyrophosphate,

N34P20'L10H20' .223 (0.50 millimol) Potassium chloride 0.44

. A mixture of C12, C14, and C tertiary aliphatic mercaptans 1n theratio of 3 :1 :1 parts by weight.

The activator composition was prepared'by dissolving 0.556 g.FeSOa'ZI-IzO, 0.894 g.

1 1 and 1.77 g. KCl in water sufficient to make 100 ml. of solution andheating the resulting mixture at 60 C. for 40 minutes. 25 ml. of thiscomposition was required to contain the requisite amounts of Theactivator composition was prepared according to the procedure given inExample IV by heating an aqueous solution of the ingredients at 60 C.for 40 minutes. Concentrations the several ingredients. Polymerizationwas ef- 5 of the materials were so adjusted that 25 ml of fectedaccording to the conventional procedure. the activator mixture containedthe quantities of A parallel run was made using the same recipe theseparate compounds listed in the recipe. A except that potassiumchloride was omitted from 62 per cent conversion was obtained in 21hours. the activator composition. The product had a Mooney value of 54.The iron Two additional runs were made using the same content of therubber was 0.013 per cent. polymerization recipe except that 6.5 partspotassium laurate was used instead of 5.0 parts. In Example VII one case0.44 part potassium chloride was present Several polymerization runs wre made to ilin the activator composition while in the other lustratethe effect of various et ods of addin case the potassium chloride wasomitted. Potassium chloride- The recipe 01 Example IV The results of thefour runs are tabulated was used with p K91 The following 1 suits wereobtained:

Conversion (percent) Percent Conversion at- K 18mm (part5) gig 20 Methodof adding KCI 1 .2: he 5 (control) none 12 21 25 31 41 i3i?$;6$?3ih? s%di $8Z13:11:31: ii 32 44 10 28 56 84 In Na4P O .FeSO complex 26 81 none13 26 33 37 45 25 In soap 21 43 44 12 33 47 63 35 Added to reactor afteractivator soln. 23 45 Added to reactor before activator soln 24 44 NoKC] 22 47 In the runs contammg potassium chloride in the activatorSystem, the conversion curves are closely linear up to 60 per centconversion. The soap Emmple VH1 concentration has 1'10 influence on thetendency Two polymerization run were made at 10 of the reaction to dieout at low initiator levels. c using the recipe f Example v In one caseThe addition of 0.44 part potassium chloride pre- 04 part 1 was added tt ferrous sulfateve s e reaction m dying O at b Soap sodiumpyrophosphate solution before heating levels- (run I) while in the otherthe KCl was added ple V after the ferrous sulfate-sodium pyrophosphateThe recipe f Example IV was employed with solution had been heated andcooled (run II). the following variations: Run I, no KCl present; mfollowmg data were run II, 0.40 part KCl added to the soap solution;tamedrun I11, 0.40 part KCl present in the activator composition. Thefollowing time-conversion Percent Conversion atdata were obtained: Run

2.5 hrs. 5.4 hrs. 7.2 hrs. 10.3 hrs. 24.0 hrs. Conversion (percent) at-Run No. 0 I 10 2e 37 54 82 2.5 hrs. 4.2 hrs. 7.6 hrs. 10.5 hrs. 23.8hrs. H 11 23 29 34 41 1g 3g These results show that the presence of KCl.in 11 27 42 s5 83 the activator during heating influences the structureor composition of the ferrous pyrophosphate These results show that theK01 must be present complex in s h a way as to imp v its efllciency asan ingredient of the activator composition if as a polymerization atothe desirable result of having reaction proceed to a high conversion inshort time is to be fully Example IX l'ealized- 55 The recipe of ExampleIV was followed for Example VI carrying out two polymerization runs at10 C. The following recipe was used for the Copolyexcept that in onecase 0.25 part sodium benzoate merization f butadiene with styrene at C.was substituted for the potassium chloride and in the other case 0.15part potassium tartrate Parts by weight was used. The results were asfollows: Butadiene 70 $$Zii 332 E] t H Methanol 48 cc m y e h Potassiumlaurate (95% 5 10mm 231m neutralized) .0 Mercaptan blend 0.2 %Z3;sittt?%g::::::13:13:: 3&3 it? 9% Cumene hydroperoxide 0.034 (0.22 millimol)None 23.9 26.1 31.9 Activator solution:

Ferrous sulfa e,

Fesorsznso 0.056 (0.2 millimol) Emmple X I Sodiu py p osphate Sodiumsalicylate (0.20 part) was substituted NasPzOmlOI-IzO 0.089 (0.2millimol) for potassium chloride in the recipe of Example Potassiumchloride 0.4 IV and polymerization carried out as before at 10 C. Thefollowing results, together with 1 See Example IV 13 those obtained froma control run in which the electrolyte was omitted, were obtained:

Conversion (percent) at- 7.5 hrs. 23.2 hrs.

Sodium Salicylate 33. 2 64. 7 Control 24. 9 32. 3

An additional run using 0.25 part sodium formate instead of potassiumchloride gave a 39.3 per cent conversion in 7.5 hours and at the end of23.2 hours a conversion of 75.5 per cent was reached.

Example XI The results show that sodium chloride exerts an optimumeffect at about 0.4 part while,

with potassium chloride about equal effects are produced over the rangefrom 0.25 to 1.00.

Example XIV Variable amounts of potassium chloride were employed in aseries of polymerization runs at 10 C. using the recipe and procedure ofExample VI. The following results were obtained:

COHVGISiQgl (percent) a KC parts 16.3 hrs. 23.4 hrs.

Example XV The copolymerization of butadiene with styrene was carriedout at 5 C. according to the fol- Example XII win r p t t Par s b wei hTwo polymerization runs were made at 10 y g Butadiene 72 C. using therecipe of Example IV except that Styrene 28 sodium sulfate wassubstituted for the potas- Water 180 5mm a a 9 2i 5 m g:Tetrahydroabietic acid, potassiurrtisalt 4.7 0 part bemg use e 0 6 OCumene hydroxide Variable lowing results were obtame Mercaptan blend 1025 I Ferrous sulfate, FeSO4.7HzO Variable 8 (mm Sulfate Conversmn(Percent) Potassium pyrophosphate, K4P2O7 Variable 0 lqmts) 0 5Potassium hydroxide 0.1 2hrs. 5hrs. 7hrs. 10.5 hrs. 24 hrs. Potassiumchloride 0 Dextrose 1.0 33333111111111: 3 :2? Z3 Example iv.

Variations in the initiator ingredients were In a third run using 0.75part sodium sulfate, shown as in the following table.

are? -m Km 1...... Run No.

Conv. Parts Millimols Parts Millimols Parts Millimols I 0. 05 0. a2 0.01 0. 25 0.08 0. 25 11 11 0. 03 0. 23 0. 05 0.18 0. 00 0.18 11 III 0. 020.14 0. 0a 0.11 0.036 0.11 is 1v 0.01 0 0s 0. 011 0. 06 0.02 0.00 15considerable retardation was observed. The reaction did not die out buta conversion of only 36 per cent was reached in 24 hours.

Example XIII Variable amounts of sodium and potassium chloride wereemployed in a series of polymerization runs at 10 C. using the recipe ofExample IV. The time-conversion data obtained were as follows:

\ Conversion (percent) at- El trol te ec y 2.5 5.2 7.0 10.6 23.5

hrs. hrs. hrs. hrs. hrs.

NaCl, 0.10 part 14 27 36 48 62 NaOl, 0.25 part 16 2% 37 77 N801, 0.40part. 11 2o 36 55 86 NaCl, 0.75 part. 1 3 4 8 7 NaCl, 1.00 part" 0 0 0 lKCl, 0.10 part. 10 26 37 54 7.1 KCl, 0.25 part." ll 28 39 59 82 KCl,0.40 part 11 29 40 53 8: KC], 0.75 part." ll 30 41 8'1 K01, 1.00 part .112 30 42 59 86 The potassium salt of tetrahydroabietic acid and 0.06part of the potassium hydroxide are dissolved together for thepreparation of the emulsifier solution. For the preparation of theactivator solution the dextrose and the remainder of the potassiumhydroxide (0.04 parts) are dissolved together in 10 parts water andheated to 71 C. for 10 minutes. The ferrous sulfate, potassiumpyrophosphate, and potassium chloride are dissolved in 10 parts waterand the mixture warmed while being mildly agitated after which it iscooled to room temperature. When the dextrose solution has cooled toroom temperature, it is added to the ferropyrophosphate solution.

For carrying out the polymerization, the emulsifier solution was chargedto the reactor after which the activator solution was added. Themercaptan, dissolved in per cent of the styrene, was then introducedfollowed by the butadiene. The contents of the reactor were brought to atemperature of 5 C. after which the cumene hydroperoxide was introducedfollowed by a rinse with the remaining 10 per cent 15 of the styrene.Polymerization was effected at C. according to the conventionaltechnique. The results obtained are shown in the table.

Example XVI Parts by weight Cumene hydroperoxide 0.06 (0.40 millimol)Ferrous sulfate,

FesO'mHzO 0.10 (0.36 millimol) Sodium pyrophosphate,

Na4P2O'z.10I-I2O 0.16 (0.36 millimol) A conversion of 31.4 per cent wasreached in 13 hours.

As will be evident to those skilled in the art, various modifications ofthis invention can be made, or followed, in the light of the foregoingdisclosure and discussion, without departing from the spirit or scope ofthe disclosure or from the scope of the claims.

We claim:

1. A process for polymerizing an organic monomeric material comprisingan unsaturated organic compound containing a CH2=C group while dispersedin an aqueous medium, which comprises polymerizing such a monomericmaterial while dispersed in an aqueous medium in the presence of anoxidant and in the presence of an activator composition prepared bydissolving in water a 'salt of a multivalent metal capable of existingin two valence states under such conditions that it is present at leastin part in a lower valence state together with a pyrophosphate of amonovalent cation selected from the class consisting of alkali metalsand ammonium and with a different salt of a monovalent cation selectedfrom the class consisting of alkali metals and ammonium and an anionwhich is inert with respect to said multivalent metal, heating saidsolution out of contact with free oxygen to a temperature between 40 and100 C. for 5 to 90 minutes and subsequently cooling the resultingsolution, and so incorporating said solution in said polymerizationalong with said oxidant that there is added, based upon 100 parts byweight of said monomeric material, 0.01 to 3 millimol parts of saidmultivalent metal, pyrophosphate and oxidant and 0.1 to 5 parts of saiddifferent salt.

2. The process of claim 1 in which said different salt is a sulfate.

3. The process of claim 1, in which said different salt is a tartrate.

4. The process of claim 1 wherein said polymerization is conducted below0 C. in the presence of an organic hydroperoxide as said oxidant.

5. The process of claim 1 in which said different salt is a fluoride ofan alkali metal.

6. The process of claim 1 in which said different salt is a chloride ofan alkali metal.

7., The process of claim 1 in which said different salt is a tetraborateof an alkali metal.

8. An improved process for producing synthetic rubber, which comprisespolymerizing a monomeric material comprising 1,3-butadiene whiledispersed in an aqueous emulsion in the presence ofdimethyl(phenyl)hydroperoxymethan as an oxidant and in the presence ofan activator composition prepared by dissolving in water ferrous rsulfate, sodium pyrophosphate and potassiumchloride, heating saidsolution out of contact with free oxygen to a temperature between 50 andC..for a period of 5 to minutes and coolin said solution, and adding thecool solution to the reaction mixture, the amount of said activatorcomposition added and the amount of said constituents present thereinbeing such that, per parts by weight of said monomeric material, thereis added 0.1 to 0.65 millimol parts each of ferrous sulfate, sodiumpyrophosphate and separately added dimethyl(phenyl) hydroperoxymethaneand 0.1 to 5 parts of potassium chloride.

9. In the catalytic polymerization of a liquid monomeric materialcomprising a conjugated diolefin while dispersed in an aqueous emulsionin which a polymerization catalyst is used comprising an oxidant and aniron pyrophosphate activator composition, the improvement whichcomprises using as an activator composition comprising said ironpyrophosphate an aqueous solution prepared by dissolving in water asoluble iron salt under conditions such that at least part of said ironis present in the ferrous state, a pyrophosphate of a monovalent cationselected from the class consisting of alkali metals and ammonium, and adifferent salt of a monovalent cation selected from the class consistingof alkali metals and ammonium and an anion which is inert with respectto ferrous and ferric ions, heating said solution out of contact with anoxidizin atmosphere to a temperature between 40 and 100 C. for 5 to 90minutes and subsequently cooling the resulting solution, and soincorporating said solution in said aqueous emulsion along with saidoxidant that there is added, based upon 100 parts by weight of saidmonomeric material, 0.01 to 3 millimol parts of iron, pyrophosphate, andoxidant and 0.1 to 5 parts of said different salt.

10. In the catalytic polymerization of a monomeric material comprising aconjugated diolefin while dispersed in an aqueous emulsion in which apolymerization catalyst is used comprising an oxidant and apyrophosphate of a multivalent metal capable of existing in two valencestates as an activator composition, the improvement which comprisesusing as said activator composition an aqueous solution prepared bydissolving in water a pyrophosphate of a monovalent cation selected fromthe class consistin of alkali metals and ammonium, a salt of such amultivalent metal under conditions such that it is present at least inpart in a lower valence state, and a different salt of a monovalentcation selected from the class consisting of alkali metals and ammoniumand an anion which is inert with respect to said multivalent metal ion,heating said solution out of contact with free oxygen to a temperaturebetween 40 and 100 C. for 5 to 90 minutes and subsequently cooling theresulting solution, and so incorporating said solution in saidpolymerization along with said oxidant that there is added, based upon100 parts by weight of said monomeric material, 0.01 to 3 millimol partsof said multivalent metal, pyrophosphate and oxidant and 0.1 to 5 partsof said dilferent salt.

11. The process of claim 10, wherein said oxidant is an organichydroperoxide, said multivalent metal is iron and is added to saidactivator solution as a ferrous salt in the absence of any reductant,and said activator composition and oxidant are separately added to saidpolymerization in such amounts that there are equimolar 17 amounts ofiron and pyrophosphate and a molar excess of said oxidant over saidiron.

12. An improved method of preparing a solution of iron pyrophosphate,which can be used as an activator solution in the polymerization of aconjugated diolefin while dispersed in an aqueous solution in thepresence of an oxidant, which comprises dissolvin in water a solubleferrous salt and a soluble pyropho'sphate in equimolar amounts and asalt of a monovalent cation selected from the class consisting of alkalimetals and ammonium and an anion which is inert with respect to ferrousand ferric ions, each in an amount between 0.5 and parts by weight per100 parts of water, and heating the resulting solution to a temperaturebetween 40 and 100 C. for 5 to 90 minutes out of contact with freeoxygen.

13. An improved method of preparing a solution of a pyrophosphate of amultivalent metal capable of existing in two valence states selectedfrom the group consisting of iron, manganese, copper, vanadium andcobalt and which can be used as an activator solution in thepolymerization of a conjugated diolefin while dispersed in an aqueousemulsion in the presence of an oxidant, which comprises dissolvin inwater a salt of said multivalent metal, capable of existing in twovalence states and under such conditions that it is present at least inpart in a lower valence state, a soluble pyrophosphate in an amount atleast stoichiometrically equivalent to said multivalent metal, and adifferent salt of a monovalent cation selected from the class consistingof alkali metals and ammonium and an anion which is inert with respectto said multivalent metal, each in an amount between 0.5 and 5 parts byweight per 100 parts of water, and heating the resulting solution to atemperature between 40 and 100 C. for 5 to 90 minutes out of contactwith an oxidizing atmosphere.

14. The method of claim 13 wherein said multivalent metal is iron, andsaid heating is at a temperature between and C. for 20 to 40 minutes.

15. As a composition of matter, an iron pyrophosphate solution preparedby dissolving in water a ferrous salt and at least an equimolar amountof a pyrophosphate and a difierent salt of a monovalent cation selectedfrom the class consisting of alkali metals and ammonium and an anioninert with respect to ferrous and ferric ions, with an amountof eachbetween 0.5 and 5 parts by weight per 100 parts of water, and heatingsaid solution to 40 to 100 C. for 5 to minutes out of contact with freeoxygen.

16. The composition of claim 15 wherein said difierent salt is afluoride.

17. The composition of claim 15 wherein said different salt is atetraborate.

18. The composition of claim 15 wherein said difierent salt is achloride.

19. The composition of claim 15 wherein said different salt is asulfate.

20. The composition of claim 15 wherein said different salt is atartrate.

CARL A. URANECK. WILLARD M. ST. JOHN. CHARLES F. FRYLING. JAMES E.TROYAN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,366,328 Fryling Jan. 2, 19452,367,877 Layng Jan. 23, 1945 2,380,614 Semon July 31, 1945 2,471,938Crouch et a1 May 31, 1949 OTHER REFERENCES Vanderberg et 2.1.: Ind. 8:Eng. Chem, vol. 40. No. 5, May 1948, pp. 932-937.

Shearon, Jr., et al.: Ind. 8: Eng. Chem., vol. 40, No. 5, May 1948, pp.769-777.

Mercks Index, 4th ed., Merck and Co., New Jersey (1930), page 281.

1. A PROCESS FOR POLYMERIZING AN ORGANIC MONOMERIC MATERIAL COMPRISINGAN UNSATURATED ORGANIC COMPOUND CONTAINING A CH2=C< GROUP WHILEDISPERSED IN AN AQUEOUS MEDIUM, WHICH COMPRISES POLYMERIZING SUCH AMONOMERIC MATERIAL WHILE DISPERSED IN AN AQUEOUS MEDIUM IN THE PRESENCEOF AN OXIDANT AND IN THE PRESENCE OF AN ACTIVATOR COMPOSITION PREPAREDBY DISSOLVING IN WATER A SALT OF A MULTIVALENT METAL CAPABLE OF EXISTINGIN TWO VALENCE STATES UNDER SUCH CONDITIONS THAT IT IS PRESENT AT LEASTIN PART IN A LOWER VALENCE STATE TOGETHER WITH A PYROPHOSPHATE OF AMONOVALENT CATION SELECTED FROM THE CLASS CONSISTING OF ALKALI METALSAND AMMONIUM AND WITH A DIFFERENT SALT OF A MONOVALENT CATION SELECTEDFROM THE CLASS CONSISTING OF ALKALI METALS AND AMMONIUM AND AN ANIONWHICH IS INERT WITH RESPECT TO SAID MULTIVALENT METAL, HEATING SAIDSOLUTION OUT OF CONTACT WITH FREE OXYGEN TO A TEMPERATURE BETWEEN 40 AND100* C. FOR 5 TO 90 MINUTES AND SUBSEQUENTLY COOLING THE RESULTINGSOLUTION, AND SO INCORPORATING SAID SOLUTION IN SAID POLYMERIZATIONALONG WITH SAID OXIDANT THAT THERE IS ADDED, BASED UPON 100 PARTS BYWEIGHT OF SAID MONOMERIC MATERIAL, 0.01 TO 3 MILLIMOL PARTS OF SAIDMULTIVALENT METAL, PYROPHOSPHATE AND OXIDANT AND 0.1 TO 5 PARTS OF SAIDDIFFERENT SALT.